Transformer



Jan. 2, 1940 s. CAMILLI TRANSFORMER '11! 11arch 1a, 1955 vi W Y v r0. M ry II. U

Inventor: Guglielmo Camilli, by 7 H 94 5M is tier-nay;

Patented Jan. 2, 1940 UNITED STATES PATENT OFFICE TRANSFORMER Guglielmo Camilli, Pittsfield, Mass., assignor to General Electric Company, a corporation of New York' Application March 18', 1938, Serial No. 196,696

3 Claims. (01. 175-361) My invention relates to transformers and its of the winding ll may of course be connected general object is to provide an improved transeither in series or in parallel. The magnetic core former construction in which the transformer is I is in the form of a long, flat strip of magnetic embedded in concrete. A concrete-encased material wound into a tight coil or helix around transformer constructed in accordance with the one side of the windings II and I2 and insulated 5 invention is fireproof and weatherproof. It may from the windings by semi-cylindrical insulating be produced very economically and has good load sheets I3. capacity because the heat conductivity of con- After the transformer core and windings are crete is good. assembled, as shown in Fig. 1, the transformer is There is a difference in the thermal expansion dried and impregnated with a suitable insulating 10 of the concrete and of the transformer parts and compound such as paraflin or other insulating this tends to cause trouble if the concrete is cast wax. A thick strip M of some cellular material directly onto the transformer and closely fits its which is pervious to a liquid but impervious to surface. The transformer should be impregnatconcrete is laid somewhere along the surface of ed with a suitable insulating compound such as the transformer, a thick strip of ordinary felt paraffin. Thermal expansion of the insulating being particularly desirable. Two or more strips compound during operation of the transformer of such material may be used and, as shown in tends to create high pressure which may rupture Figs. 2 and 3, the strip I 4 of cellular material is the concrete casing, and the principal object of shown along the surface of one of the windings the invention is to provide an arrangement which and an additional strip of cellular material i5 is n will permit such expansion of the insulating comshown along the surface of the core 10. The pound without injury to the concrete. The insutransformer surface covered by the felt or other iating compound may soften and become liquid cellular material is so restricted, however, as under temperature conditions prevailing during shown in Figs. 2 and 3, as to prevent any substanoperation of the transformer but it may be solid tial interference to heat dissipation from the :3

under low temperature conditions such as prevail transformer. during light load conditions and when operation A sealed casing ii of concrete is cast in one of the transformer is first started. piece around the transformer and the cellular Difference in thermal expansion and contracstrips l4 and I5 and closely fitting the surface tion when the insulating compound is solid may of the transformer as indicated in Figs. 2 and 3. cause empty spaces to appear between the trans- The insulating compound with which the transformer and the concrete so that high voltages in former was impregnated prevents moisture from the transformer windings might cause some the concrete from entering and wetting the transcorona and the invention is therefore particuformer where it would be apt to cause rusting of larly applicable in connection with transformers the core and lowering of the dielectric strength of which operate at low or medium voltages. the winding insulation. After the concrete has The invention will be better understood from hardened, it is thoroughly dried preferably by the following description taken in connection heating it in a partial vacuum. with the accompanying drawing in which Fig. 1 The paraflin or other insulating compound 40 shows a transformer before it has been provided with which the transformer is impregnated will 40 with its concrete casing; g. 2 is a view partly in expand under high temperature conditions dursection of the transformer enclosed in concrete ing operation of the transformer and under these in accordance with the invention; and Fig. 3 is :1 conditions the compound will soften and may sectional view on the line 3-3 of Fig. 2. even become a liquid. Thus it can flow readily Like reference characters indicate similar as it expands. The concrete was excluded from 45 parts of the diiferentfigures of the drawing. the spaces occupied by the felt strips l4 and IS The invention is particularly applicable in conand the softened or liquid parailin expands readnection with transformers of rather small size so fly into the cellular spaces in the felt so that exthat the weight of the concrete casing may not be cessive pressure inside the sealed concrete casobjectionable, such a transformer being indicated ing l6.,cannot occur. 5 in Fig. l and including a magnetic core I II pro- The concrete casing l6 has good heat conducvided with windings Ii and II. In the particutivity so that the heat generated by the losses in lar'transformer shown in the drawing the windthe transformer is rapidly dissipated and the load ing H is formed in two sections disposed at oppocapacity of the transformer is consequently good.

site sides of the winding I 2. These two sections A transformer may be constructed in accordance u with the invention with very little labor and with inexpensive materials.

The invention has been explained by describing a particular. transformer structure produced in accordance with the invention-and it will be apparent that changes may be made without departing from the spirit of the invention and the scope of the appended claims.

'What I claim as new and desire to secure by Letters Patent of the United States, is:

l. The combination with a transformer treated with an insulating compound which softens when heated, of a sealed one piece concrete casing closely fitting the surface of the transformer, and a cellular member between the transformer surface and the concrete to permit thermal expansion of the insulating compound, the transformer surface covered by the cellular member being restricted to prevent any substantial interference to heat dissipation from the transformer.

2. The combination with a transformer treated with an insulating compound which softens when heated. of a sealed one piece concrete casing closely fitting the surface of the transformer, and a felt member between the transformer surface and the concrete to permit thermal expansion of the insulating compound, the transformer surface covered by the felt member being restricted to prevent any substantial interference to heat dissipation from the transformer.

3. The combination with a transformer treated with insulating wax which softens when heated, of a sealed one piece concrete casing closely fltting the surface 'of the transformer, and a felt member between the transformer surface and the concrete to permit thermal expansion of the wax, the transformer surface covered by the felt member being restricted to prevent any substantial interference to heat dissipation from the trans-' former.

GUGLIEIMO CAMILLI. 20 

